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The A-B-C Model of Tooth Decay: How Cavities Develop and What We Can Do to Prevent Them

What is a cavity?
Simply stated, a cavity is a hollow place in a tooth caused by decay. Cavities form when certain bacteria are exposed to simple carbohydrates, producing an acid that dissolves the outside of the tooth.

To illustrate, I like to use an A-B-C model of tooth decay—each of these elements is necessary for a cavity to occur:

A = Tooth
B = Bacteria
C = Carbohydrates

If you take away any of these three elements, you take away the possibility for a cavity.

A = Tooth
Teeth are made up of three components: enamel, dentin and pulp. The enamel is the tooth's protective layer, a white coating that is very strong and dense. Dentin, the middle layer, is not as hard and more yellow in color. The pulp is the center part and the nerve of the tooth.

Enamel, the Tooth's Bricks and Mortar
If you examined enamel under a microscope, you would see something like a brick wall with mortar holding the bricks in place. If the pH of your mouth (a measure of acidity and alkalinity) reaches a high acidic level for a lengthy period of time, some of the tooth's 'mortar' begins to dissolve. When too much mortar is lost, bricks start to fall out.

When bacteria in the mouth is fed foods containing simple sugars or starch, an acid that dissolves tooth enamel may create a hole. Bacteria move into the hole as it forms, producing more acid, lowering the pH level and making the tooth enamel even more susceptible to the dissolving acid.

B = Bacteria
Many different types of bacteria live in our mouths, some good and some not so good. One type of not-so-good bacteria is strep mutans, usually found on the tooth's outer layer. In the presence of a simple carbohydrate such as sugar, strep mutans can cause an acidification of dental plaque. If the pH in the saliva gets down to 5.2 or lower (7.0 is neutral), tooth enamel can de-mineralize, or weaken.

When bacterial acid assaults a tooth for an extended period of time, a hole may develop in the tooth's enamel wall. This hole provides the perfect hiding place for bacteria, which continues producing acid and dissolving into the next layer of the tooth, starting a cavity.

C = Carbohydrates
Carbohydrates are necessary for your child's growth and development. However, simple carbohydrates such as candy, cookies and sweet cereals can result in acid production that is immediately harmful to teeth. Complex carbohydrates such as grains and vegetables are good for teeth because they take longer to break down. As a result, the acids are produced in the stomach, rather than in the mouth.

Did you know that the average child is exposed to acid on tooth enamel for two hours every day? With each exposure to simple carbohydrates such as sugar and starch, bacteria produce acid for about twenty minutes. Most children eat three meals, plus three snacks daily, resulting in acid exposure for two hours!

Here are some tips for preventing cavities in your child's teeth:

Try to keep your child's teeth as bacteria-free as possible with regular brushing, flossing or wiping. Cleaning teeth three times a day is an important habit that keeps bacteria and acid levels low.

Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.